1. Field of the Invention
The invention relates to a wristwatch with the function of sensing heart pulses, and more particularly, to a wristwatch having a first electric terminal on a bottom cover to permit a close contact with the wrist of one hand and a second electric terminal on the front side of the wristband for two fingers of another hand to touch thereon. Accordingly, the accuracy in measuring the heart pulse rate is reinforced.
2. Description of the Related Art
Generally, the heart pulses significantly varies during an exercise session. It is essential to monitor the heart pulse rate during the exercise session since the greatest benefit from exercise occurs when the heart pulse rate rises to 60% of the maximal rate. In exceeding this percentage, it will be harmful to the human body. Accordingly, to facilitate the measuring action and to provide accurate readings are important to the health during the exercise session.
Conventional heart pulse sensors are of various types and forms. U.S. Pat. No. 4,409,983, U.S. Pat. No. 4,224,948, U.S. Pat. No. 4,120,269 and U.S. Pat. No. 5,807,267 teach different kinds of pulse-sensing watches while the employed sensors are selected from the group consisting of infrared sensors, exhaust sensors, piezo pressure sensors, and optical sensors. Due to the influence of various external factors, the accuracy of the infrared sensor leaves much to be desired. As for the sensor detecting the voltage frequency change during blood circulation, the detection interface in contact with the human body has to be taken into account. If the detection interface is not able to ensure an effective contact with the human body, the measured heart pulse rate may be inaccurate. For example, in taking a metal surface as the detection interface, the contact will be unstable due to the slippery metal surface when the skin with perspiration is in contact with the interface. Accordingly, the accuracy will be seriously affected.
U.S. Pat. No. 5,807,267 teaches a heart pulse rate monitor assembly with sensor means mounted on a bottom side of a wristband for sensing heart pulses of the radial artery of the user. The assembly includes a piezo pressure sensor or an optical sensor adjacent to the radial artery for sensing the heart pulses thereof. The disadvantages thereof lie in that the measured result is easily influenced by external factors. Meanwhile, whether the detecting position is correct or not plays a significant part in the accurate readings. This apparatus may be suitable for medical professionals like physicians, nurses, etc. However, it is much difficult for normal persons to exactly locate the radial artery for an accurate detection of the heart pulses.
In addition to the convenient use, how to improve the sensing accuracy is also the main consideration of the invention.